High-speed, 3-D method and system for optically inspecting parts

ABSTRACT

A high-speed, 3-D method and system for optically inspecting parts are provided. The system includes a part transfer subsystem including a transfer mechanism adapted to support a part at a loading station and transfer the supported part from the loading station to an inspection station at which the part has a predetermined position and orientation for inspection. The system also includes an illumination assembly to simultaneously illuminate an end surface of the part and a peripheral surface of the part. The system further includes a lens and detector assembly to form an optical image of the illuminated end surface and an optical image of the illuminated peripheral surface of the part and to detect the optical images. The system still further includes a processor to process the detected optical images to obtain an end view of the part and a 3-D panoramic view of the peripheral surface of the part.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/414,081 filed Mar. 7, 2012.

TECHNICAL FIELD

This invention relates in general to the field of the non-contact,optical inspection of parts and, more particularly, to high-speed, 3-Dmethods and systems for optically inspecting parts, such as threadedfasteners.

OVERVIEW

Traditional manual, gauging devices and techniques have been replaced tosome extent by automatic inspection methods and systems. However, suchautomatic inspection methods and systems still have a number ofshortcomings associated with them.

Many parts, such as fasteners, are cold formed from wire stock.Oftentimes a crack or split results in the head of the part or fastenerduring such cold forming. Such cracks or splits can appear not only inthe top surface of the head but also in the peripheral side surfaces ofthe head. Multiple cameras can be used to image these surfaces but thatincreases cost and space requirements of the inspection system. Also,the parts can be rotated about their axes but this adds additional timeto the inspection process.

Metering wheels are often used in optical part inspecting and sortingsystems. Such wheels separate the parts and can feed the separated partson a “Vee” track. Prior metering wheels are typically made of UHMW orDelrin plastic.

Pericentric or hypercentric lenses suffer from cost, weight and sizeissues. As a result, linescan products are most commonly used to imagefasteners: Linescan provides high resolution, distortion free images andgood control over illumination. However, linescan-based systems alsosuffer from technical and cost concerns; parts to be inspected must bebrightly illuminated and rotated within the camera's field of view(FOV).

U.S. Pat. No. 7,403,872 discloses a method and system for inspectingmanufactured parts such as cartridges and cartridge cases and sortingthe inspected parts.

WO 2005/022076 discloses a plurality of light line generators whichgenerate associated beams of light that intersect a part to beinspected.

U.S. Pat. No. 6,313,948 discloses an optical beam shaper for productionof a uniform sheet of light for use in a parts inspection system havinga light source including a coherent light generator, a diffractive beamshaper, and lens elements.

U.S. Pat. No. 6,285,034 discloses an inspection system for evaluatingrotationally asymmetric workpieces for conformance to configurationcriteria.

U.S. Pat. No. 6,252,661 discloses an inspection system for evaluatingworkpieces for conformance to configuration criteria.

U.S. Pat. No. 6,959,108 discloses an inspection system whereinworkpieces to be inspected are consecutively and automatically launchedto pass unsupported through the field of view of a plurality of cameras.

U.S. Pat. No. 4,831,251 discloses an optical device for discriminatingthreaded workpiece by the handedness by their screw thread profiles.

U.S. Pat. No. 5,383,021 discloses a non-contact inspection systemcapable of evaluating spatial form parameters of a workpiece to provideinspection of parts in production.

U.S. Pat. No. 5,568,263 also discloses a non-contact inspection systemcapable of evaluating spatial form parameters of a workpiece to provideinspection of parts in production.

U.S. Patent Application Publication No. 2005/0174567 discloses a systemto determine the presence of cracks in parts.

U.S. Patent Application Publication No. 2006/0236792 discloses aninspection station for a workpiece including a conveyor, a mechanism forrotating the workpiece, and a probe.

Other U.S. patent documents related to the invention include: U.S. Pat.Nos. 6,787,724; 6,995,837; 7,164,783; 7,245,759; 7,491,319; 7,669,707;and 7,801,692.

SUMMARY OF EXAMPLE EMBODIMENTS

An object of at least one embodiment of the present invention is toprovide a high-speed, 3-D method and system to optically inspect partswithout the need for multiple cameras and without the need for partrotation thereby providing a compact, cost-effective and simplersolution to the inspection task.

In one example embodiment, a high-speed, 3-D method of opticallyinspecting parts is provided. The method includes the steps ofsupporting a part to be inspected at a loading station and transferringthe supported part so that the part travels along a first path whichextends from the loading station to an inspection station at which thepart has a predetermined position and orientation for inspection. Themethod further includes simultaneously illuminating an end surface ofthe part and a peripheral surface of the part at the inspection stationand forming an optical image of the illuminated end surface and anoptical image of the peripheral surface of the part at a single imageplane at the same time. The method also includes detecting the opticalimages at the image plane and processing the detected optical images toobtain an end view of the part and a 3-D panoramic view of theperipheral surface of the part. The method still further includestransferring the part after the inspection at the inspection station sothat the inspected part travels along a second path which extends fromthe inspection station to an unloading station.

The optical image of the illuminated end surface may be formed at acentral portion of the image plane and the optical image of theperipheral surface may be formed around the central portion at the imageplane.

The peripheral surface may be an outer peripheral surface which extends360° around the part.

The loading station may be spaced away from the unloading station.

The method may further include the step of coordinating the inspectionof the part at the inspection station with the transfer of the part toand from the inspection station to control movement of the part and theinspecting of the part.

The first and second paths may define a curved path wherein each of thestations is located along the curved path.

The method may further include processing the detected images toidentify a defective part.

The radiation may be visible light radiation.

The parts may have heads wherein the end surface is a top surface of thehead and wherein the peripheral surface is a peripheral surface of thehead.

The detected optical images of the head may be processed to determine ahead crack or split.

The parts may be fasteners.

In another example embodiment, a high-speed, 3-D system for opticallyinspecting parts is provided. The system includes a part transfersubsystem including a transfer mechanism adapted to receive and supporta part at a loading station and to transfer the supported part so thatthe part travels along a first path which extends from the loadingstation to an inspection station at which the part has a predeterminedposition and orientation for inspection. The transfer mechanismtransfers the part after inspection at the inspection station so thatthat the inspected part travels along a second path which extends fromthe inspection station to an unloading station. The system also includesan illumination assembly to simultaneously illuminate an end surface ofthe part and a peripheral surface of the part. The system furtherincludes a lens and detector assembly to form an optical image of theilluminated end surface and an optical image of the illuminatedperipheral surface of the part and to detect the optical images. Thesystem further includes a processor to process the detected opticalimages to obtain an end view of the part and a 3-D panoramic view of theperipheral surface of the part.

The lens and the detector assembly may include a hypercentric orpericentric lens subsystem. The lens subsystem may provide a converging3-D panoramic view of the peripheral surface of the part.

The peripheral surface may be an outer peripheral surface which extends360° around the part.

The detector may include an image sensor having an image plane to detectthe optical images.

The illumination assembly may include at least one source of radiation.

The parts may have heads wherein the end surface is a top surface of thehead and the peripheral surface is a peripheral surface of the head.

The detected optical images may be processed to determine a head crackor split.

The parts may be fasteners.

The optical image of the illuminated end surface may be formed at acentral portion of the image plane and the optical image of theperipheral surface may be formed around the central portion at the imageplane.

The transfer mechanism may include a metering wheel.

The at least one source of radiation may include a backlight wherein thetransfer mechanism is disposed between the lens and detector assemblyand the backlight at the inspection station.

The metering wheel may be an optically transparent to permit the part tobe imaged by the backlight through the metering wheel.

In yet another example embodiment, a high-speed, 3-D system foroptically inspecting fasteners is provided. Each of the fasteners has ahead. The system includes a fastener transfer subsystem including atransfer mechanism adapted to receive and support a plurality offasteners at their heads in spaced apart relationship at a loadingstation and to transfer the supported fasteners so that the fastenerstravel along a first path which extends from the loading station to aninspection station at which the fasteners have a predetermined positionand orientation for inspection. The transfer mechanism transfers thefasteners after the inspection at the inspection station so that theinspected fasteners travel along a second path which extends from theinspection station to an unloading station. The system further includesan illumination assembly to simultaneously illuminate a top surface ofthe head and an entire peripheral surface of the head when the fasteneris located at the inspection station. The system also includes ahypercentric or pericentric lens and detector assembly to form anoptical image of the illuminated top surface and an optical image of theentire peripheral surface of the head and to detect the optical images.The system still further includes a processor to process the detectedoptical images to obtain a top view of the head and a 3-D panoramic viewof the entire peripheral surface of the head and to determine a headcrack or split.

The peripheral surface may be an outer peripheral surface.

Other technical advantages will be readily apparent to one skilled inthe art from the following figures, descriptions and claims. Moreover,while specific advantages have been enumerated, various embodiments mayinclude all, some or none of the enumerated advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective environmental view of at least one embodiment ofa high-speed, 3-D system for optically inspecting parts;

FIG. 2 is an enlarged top side perspective, block diagram view,partially broken away, of the system of FIG. 1;

FIG. 3 is a top side perspective block diagram view, partially brokenaway, and opposite the side of FIG. 2 of the system of FIGS. 1 and 2;

FIG. 4 is a back side perspective block diagram view of the system ofFIGS. 1, 2 and 3;

FIG. 5 is a block diagram schematic view of the system of FIGS. 2-4 withits metering wheel at inspection, loading and unloading stations;

FIG. 6 is a side schematic view, partially broken away, of ahypercentric or pericentric lens and supported ring light with an objectpositioned within the near viewing cone (NVC) of the lens; and

FIG. 7 shows top and side converging views of an object (here a dice) asit will appear at an image plane of an optical detector or camera afterimaging through the lens of FIG. 6.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

In general, one embodiment of the high-speed, 3-D method and system ofthe present invention optically inspects manufactured parts such asfasteners or bolts illustrated in FIGS. 2-6. The inspected parts arethen typically sorted based on the inspections. The system is designedfor the inspection of the heads of such bolts for splits and/or cracks.However, the system is also suitable for other small, mass-producedmanufactured parts where external splits and cracks are of concern. Thesubsystems which may be used for part handling and delivery may varywidely from application to application depending on part size and shape,as well as what inspections are being conducted. The subsystemsultimately chosen for part handling and delivery have some bearing onthe nature of the subsystem or system conducting the optical inspection.

Initially, parts, such as bolts 10 (FIGS. 2-6), are placed into a feederbowl 12 having a scalloped rim 14. The bowl 12 is supported on anadjustable frame structure 11. Tooling around the rim 14 takes advantageof the asymmetrical mass distribution of the bolts 10 to feed the bolts10 onto a downwardly sloped vibratory feeder conveyor or loader 16.Consequently, every bolt 10 which exits the bowl 12 is received by theconveyor 11 and is oriented in the same direction as shown in FIGS. 2and 3. One or more vibrators controlled by a vibrator controller (FIG.5) vibrate the bowl 12 and the conveyor 11 to help move the bolts 10 insingle file to a loading station (FIG. 5). At the loading station thelongitudinal axes of the bolts 10 are substantially parallel.

At the loading station, a part transfer subsystem, generally indicatedat 18, of a high-speed, 3-D system 20 for optically inspecting parts isprovided to transfer the bolts from the loading station, to aninspection station and then to an unloading station. The subsystem 18includes a transfer mechanism in the form of metering wheel 22 which is,preferably, made of an optically transparent plastic material such asacrylic so that heads 13 of the bolts 10 (FIGS. 5 and 6) can bebacklight only or backlight/frontlight simultaneously during imaging asdescribed in detail herein below. If the inspection application needs ablack or white background, a different wheel can be chosen for thedifferent colored bolt head.

The wheel 22 has openings 24 formed about its outer peripheral surfacewhich are adapted to receive and support the bolts 10 at the loadingstation and to transfer the supported bolts 10 so that the bolts 10travels along a first path indicated by an arrow 25 which extends fromthe loading station to an inspection station (FIG. 5) at which each bolt10 has a predetermined position and orientation for optical inspection.The bolts 10 are supported on the wheel 22 during wheel rotation by astationary guide 26. The wheel 22 is rotated by an electric motor 28under the control of a motor controller 30 to rotate about an axis 34(FIG. 5).

At the inspection station, each bolt axis is aligned with an opticalaxis of a hypercentric or pericentric lens as described in detail below.Consequently, axial or on-axis machine vision viewing is provided. Afterinspection, the wheel 22 transfers the bolts 10 from the inspectionstation so that the inspected bolts 10 travel along a second path whichextends from the inspection station to an unloading station where thenow unsupported bolts 10 fall under the force of gravity.

The system 20 also includes an illumination assembly to simultaneouslyilluminate an end surface 36 of each bolt head 13 and an outerperipheral surface 38 of each bolt head 13. The illumination assemblytypically includes an LED ring light 40 (FIG. 6) on or adjacent a lensand detector assembly, generally indicated at 42, and which has anoptical axis. The illumination assembly also typically includes abacklight 44 which illuminates the bolt heads 13 through the opticallytransparent wheel 22.

The lens and detector assembly 42 forms an optical image of theilluminated end surface 36 and a converging optical image of theilluminated peripheral surface 38 of the bolt head 13 and detects theoptical images. The assembly 42 includes a detector in the form of animage sensor having an image plane to detect the optical images.

The assembly 42 preferably has a pericentric or hypercentric lenssubsystem 46 wherein the lens subsystem provides a converging 3-Dpanoramic view of the outer peripheral surface 38 of each bolt head 13.The surface 38 extends 360° around the bolt head 13. For illustrativepurposes only, FIG. 7 shows an imaged peripheral surface of a die havingfaces “3”, “5”, “4” and “2” which surround a top surface of the dieface, “6”.

The system 20 also includes a video processor 50 to process the detectedoptical images to obtain an end view of the bolt head 13 and a 3-Dpanoramic view of the peripheral surface 38 of the bolt head 13. Thedetected optical images are processed by the processor 50 to determine ahead crack or split. The processor 50 determines if a significant crackor split is present by seeing if the imaged light is discontinuous at aposition corresponding to the crack location.

The system 20 also includes a system controller 52 which controls andcoordinates the inspection of bolts 10 at the inspection station withthe transfer of the bolts 10 and from the inspection station to controlmovement of the bolts 10 and the inspection of the bolts 10. The resultsof the processing by the processor 50 are output to the systemcontroller 52 which controls the system 20 based on the results of theoptical inspection. Sensors 54 provide various timing or positionsignals to the controller 52 to help control the system 20. For example,one type of sensor may signal the controller 52 when the bolts 10 arelocated at or near the inspection station in the system 20 so that thelens and detector assembly 42 can be controlled by the controller 52 totake “pictures” of the bolt heads 13 at the inspection station.

The system 20 may also include a display and a user interface (FIG. 5)to permit two-way user interaction with the system 20.

After inspection at the inspection station, the bolts 10 may be droppedonto a track 56 which may take the form of an AMPCO 18 oriented at a 35°angle. As the bolts 10 slide down the track 56, they may pass throughother inspection stations to be inspected one at a time. Bolts 10 whichpass each of the inspections may be actively accepted by a part diverteror flipper (not shown) located at the bottom of the track 56.

Referring now to FIG. 6, there are illustrated specifications for onetype of hypercentric lens subsystem entitled “Hyper-Eye” available fromLight Works, LLC of Toledo, Ohio. Hyper-Eye hypercentric lenses providea converging view as if aimed at a single point called the ConvergencePoint (CP). The lenses can also provide a top view. The distance to thispoint is called the Convergence Point Distance (CPD).

The volume that can actually be well-imaged is contained within animaginary truncated cone called the New View Cone (NVC). This is thehatched region of FIG. 6. The dimensions of this region are T, B and MaxWD; WD is the distance from the lens 46 to the top surface 36 of thebolt head 13; these will vary for different lens models.

An additional parameter of Hyper-Eye lenses is the Maximum View Angle(MVA). This is the largest angle of the NVC. Rays of light from anobject are collected over a broad range of angles, up to the limit ofthe MVA. Outside this angle, nothing is imaged.

The rays of light collected from the bolt head 13 are imaged at thedetector. Larger ray angles correspond to larger image radii. Thiscorrespondence or Angle to Image Mapping (AIM) varies with the lensmodel. Obviously, other types of hypercentric lenses could also be used.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A system for inspecting parts of the type formed with a head having an end surface and a peripheral surface, the system comprising: a first transfer mechanism adapted to transfer a part to an inspection station; a light source to illuminate the end surface of the part and the peripheral surface of the part at the inspection station; an optical device to simultaneously image the illuminated end surface of the head and the illuminated peripheral surface of the head in a single image plane when the part is at the inspection station; and a second transfer mechanism to route the part from the inspection station based on images of the end and peripheral surfaces of the head in the single image plane, wherein the first transfer mechanism includes a metering wheel, and the metering wheel is optically transparent to permit the part to be imaged by a backlight through the metering wheel.
 2. The system of claim 1, wherein the optical device includes a lens and detector assembly.
 3. The system of claim 2, wherein the lens and detector assembly includes a hypercentric or pericentric lens subsystem and wherein the lens subsystem provides a converging 3-D panoramic view of the peripheral surface of the head.
 4. The system of claim 2, wherein the detector assembly includes an image sensor having the image plane to detect the optical images.
 5. The system of claim 1, wherein the image of the illuminated end surface is formed at a central portion of the image plane and the image of the peripheral surface is formed externally of the central portion of the image plane.
 6. The system of claim 1, wherein the light source includes a backlight, and wherein the first transfer mechanism is disposed between the optical device and the backlight at the inspection station. 